There are a number of patents and publications relating to the decomposition of aluminum nitrate. In U.S. Pat. No. 1,702,410 (Feb. 10, 1931) to Max Buchner, it is stated (p. 3, line 75-83)--"The decomposition of aluminum nitrate may be effected by heating it in the solid, crystallized or dissolved state, or in the state in which it occurs after the last step in the process, if desired, with the introduction of gases, or of water or steam. In this way nitric acid of any desired concentration can be produced." The patent goes on to say (p. 3, line 102-105)--"In this way about 92% of the nitric acid in the aluminum nitrate can be recovered; therefore, nitrous gases are formed only in small quantity."
U.S. Pat. No. 2,737,445, issued Mar. 6, 1956 in the name of Ernest Samuel Nossen describes a process for the thermal decomposition of metal nitrates including aluminum nitrate. The process involves the addition of steam (and other gases) to form nitric acid vapors for recovery of nitric acid in liquid form. In this patent, the starting material could be either solid or aqueous metal nitrate.
Other patents and publications describing the decomposition of metal nitrates include German Pat. No. 556,882, issued to Dr. Fritz Gewecke on Aug. 15, 1932 and two articles by this same Dr. Gewecke, one in Die Chemical Fabrik No. 21-22, pp. 199-209 (1934), the other in Chemiker-Zeitung, No. 15, pp. 157-58 (1936). The Gewecke patent and publications disclose the complete thermal decomposition of aluminum nitrate by (a) heating the metal nitrate in the form of a thin film to a temperature higher than the temperature of its decomposition, (b) in the presence of steam to obtain a solid product and substantially complete recovery of all nitric acid.
Several publications by the Atomic Energy Commission describe the practice of decomposition of aluminum nitrate. These publications also describe in considerable detail, equipment used in such decomposition. Among the publications of interest are the following by the Atomic Energy Division of Phillips Petroleum Company, Idaho Falls, Idaho: "Pneumatic Atomizing Nozzles in Fluidized Bed Calcining, Part I-Calibration Tests" by Legler and Stevens, IDO-14548, TID-4500, Ed. 16, and "Pneumatic Atomizing Nozzles in Fluidized Bed Calcining-Part II Process Tests" by Leglar and Brown, IDO-14631, TID-4500 (32st Edition), issued July 1964. The latter report describes decomposition tests of aluminum nitrate waste solutions in a fluidized bed calciner with considerable description of feed nozzle selection and operation. Particle size control is discussed in detail. Similar information is reported by Legler in an article published in "Chemical Engineering Progress" in February 1967 titled "Feed Injection for Heated Fluidized Beds." Earlier, Cooper and Black of Phillips Petroleum, Idaho Falls, Idaho, had published "Pilot-Plant-Scale Fluidized Bed Calciners," CEP (Vol. 61, No. 7, July 1965). The kinetics of particle growth in fluidized bed calcination of aluminum nitrate solutions (radioactive waste liquor from nuclear fuel reprocessing) was investigated by Lee et al. in "Kinetics of Particle Growth in A Fluidized Calciner," AIChE Journal, Vol. 8, No. 1, March 1962, pp. 53-58. The AEC publications referenced earlier give various references to earlier work at Idaho, the earliest cited being--Crimet, E.S. "Calcination of Aluminum-Type Reactor Fuel Wastes in a Fluidized Bed," IDO-14416, August 1957. U.S. Pat. No. 3,869,543 (Mar. 4, 1975), and U.S. Pat. No. 3,898,043 (Aug. 5, 1975) in the names of Schutte and Stevens, assigned to Arthur D. Little, Inc. describes a method and apparatus, respectively, for decomposition of aqueous aluminum nitrate solution to form an alumina product and nitric acid. The apparatus described is a conventional fluidized bed design with indirect heating coils. One notable feature of the heating tubes described in the patent is their U-tube arrangement in the fluidized bed design with indirect heating coils. Such an arrangement would be impractical for using a condensing heat transfer fluid, such as steam, due to difficulty in withdrawing the condensate.
The A.D. Little U.S. Pat. No. 3,869,543 describes aluminum nitrate decomposition in a method using at least two separate beds of fluidized particles and fluidizing the bed particles of one of the beds with steam, while using the off-gases effluent from one bed fluidized with steam as the fluidizing gas for the remaining beds. There is also described the separation of off-gases into nitric acid and water vapor containing noncondensable oxides of nitrogen and the subsequent condensing of the water vapor thereby removing the oxides of nitrogen. There is no mention of recovering of the heat of condensation from the condensing of nitric acid and water vapor. In U.S. Pat. No. 3,898,043, the production of a material presenting no handling problems is stated as an objective. The patent discusses problems reported in the prior art of handling a sticky, glue-like material formed during the hydrolysis process. The A.D. Little patent purports to resolve this problem by an improved decomposition process. The A.D. Little patent admits to prior patents using steam for hydrolysis to recover substantially all the nitrate values from decomposition as nitric acid, but states that the problems of the prior art are overcome (col. 3, line 2. U.S. Pat. No. 3,898,043). This is supposedly done by feeding an aluminum nitrate solution corresponding to the composition of melted AL(NO.sub.3).sub.3.9H.sub.2 O ANN crystals into a fluidized bed, which is maintained at a temperature between about 150.degree. and 210.degree..
A number of publications exist relating to fluidized bed design and operation. Of particular interest are those by F. A. Zenz, such as "How Flow Phenomena Affect Design of Fluidized Beds," Chemical Engineering, Dec. 19, 1977, pp. 81-91. In this article, Dr. Zenz teaches the concept of jet penetration into particle beds as the critical consideration in preventing scale formation on the nozzle and providing adequate atomization.